Currently, a mainstream process of mass production of an organic electroluminescent device (e.g., an Organic Light-Emitting Diode (OLED)) is a vacuum thermal evaporation process, i.e., an organic material is heated, gasified and then uniformly deposited on a substrate under a high vacuum condition. By using the vacuum thermal evaporation process, an anode, a hole injection layer (HIL), a hole transport layer (HTL), an emission layer (EML), an electron transport layer (ETL), an electron injection layer (EIL) and a cathode are sequentially formed on the substrate. However, the vacuum thermal evaporation process requires relatively expensive cost for a vacuum process and an evaporation mask and the like, and a material utilization ratio in the vacuum thermal evaporation process is extremely low. In order to solve these problems, a solution process is proposed to prepare the OLED device, i.e., the substrate is coated in a solution mode, so as to sequentially form the above layers of the OLED device and to reduce the fabrication cost. However, there are still many problems in the solution process. For example, solvents are used in the solution process; in the case that a plurality of film layers have been formed and then the solvent for other film layer is coated thereon, it is likely that the film layers that have been dried and finally formed are dissolved, such that the respective layers of the OLED device blend with one another and a waste product is resulted.
Therefore, it is proposed that the OLED device is prepared by the solution process and the vacuum thermal evaporation process, i.e., several film layers (e.g., the anode, the HIL and the HTL) are prepared by using the solution process firstly, and then the remaining film layers (e.g., the EML, the ETL, the EIL and the cathode) are prepared by using the vacuum thermal evaporation process. In this way, the fabrication cost is reduced to some extent and the efficiency and yield are improved to some extent.
However, at the heterogeneous interface between the film layer (e.g., the HTL) prepared by using the solution process and the film layer (e.g., the EML) prepared by using the vacuum thermal evaporation process, there are many defects (e.g., impurities, pores, etc.) generated due to the switch of processes, which seriously affects light emission efficiency of the OLED device and greatly reduces a service life of an OLED display panel.